1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2019 SUSE
3 
4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
5 
6 #include <linux/slab.h>
7 #include <linux/module.h>
8 #include <linux/kernel.h>
9 #include <linux/printk.h>
10 #include <linux/livepatch.h>
11 
12 #define CONSOLE_LOGLEVEL_STATE 1
13 /* Version 1 does not support migration. */
14 #define CONSOLE_LOGLEVEL_STATE_VERSION 1
15 
16 static const char *const module_state[] = {
17 	[MODULE_STATE_LIVE]	= "[MODULE_STATE_LIVE] Normal state",
18 	[MODULE_STATE_COMING]	= "[MODULE_STATE_COMING] Full formed, running module_init",
19 	[MODULE_STATE_GOING]	= "[MODULE_STATE_GOING] Going away",
20 	[MODULE_STATE_UNFORMED]	= "[MODULE_STATE_UNFORMED] Still setting it up",
21 };
22 
23 static void callback_info(const char *callback, struct klp_object *obj)
24 {
25 	if (obj->mod)
26 		pr_info("%s: %s -> %s\n", callback, obj->mod->name,
27 			module_state[obj->mod->state]);
28 	else
29 		pr_info("%s: vmlinux\n", callback);
30 }
31 
32 static struct klp_patch patch;
33 
34 static int allocate_loglevel_state(void)
35 {
36 	struct klp_state *loglevel_state;
37 
38 	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
39 	if (!loglevel_state)
40 		return -EINVAL;
41 
42 	loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL);
43 	if (!loglevel_state->data)
44 		return -ENOMEM;
45 
46 	pr_info("%s: allocating space to store console_loglevel\n",
47 		__func__);
48 	return 0;
49 }
50 
51 static void fix_console_loglevel(void)
52 {
53 	struct klp_state *loglevel_state;
54 
55 	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
56 	if (!loglevel_state)
57 		return;
58 
59 	pr_info("%s: fixing console_loglevel\n", __func__);
60 	*(int *)loglevel_state->data = console_loglevel;
61 	console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
62 }
63 
64 static void restore_console_loglevel(void)
65 {
66 	struct klp_state *loglevel_state;
67 
68 	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
69 	if (!loglevel_state)
70 		return;
71 
72 	pr_info("%s: restoring console_loglevel\n", __func__);
73 	console_loglevel = *(int *)loglevel_state->data;
74 }
75 
76 static void free_loglevel_state(void)
77 {
78 	struct klp_state *loglevel_state;
79 
80 	loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
81 	if (!loglevel_state)
82 		return;
83 
84 	pr_info("%s: freeing space for the stored console_loglevel\n",
85 		__func__);
86 	kfree(loglevel_state->data);
87 }
88 
89 /* Executed on object patching (ie, patch enablement) */
90 static int pre_patch_callback(struct klp_object *obj)
91 {
92 	callback_info(__func__, obj);
93 	return allocate_loglevel_state();
94 }
95 
96 /* Executed on object unpatching (ie, patch disablement) */
97 static void post_patch_callback(struct klp_object *obj)
98 {
99 	callback_info(__func__, obj);
100 	fix_console_loglevel();
101 }
102 
103 /* Executed on object unpatching (ie, patch disablement) */
104 static void pre_unpatch_callback(struct klp_object *obj)
105 {
106 	callback_info(__func__, obj);
107 	restore_console_loglevel();
108 }
109 
110 /* Executed on object unpatching (ie, patch disablement) */
111 static void post_unpatch_callback(struct klp_object *obj)
112 {
113 	callback_info(__func__, obj);
114 	free_loglevel_state();
115 }
116 
117 static struct klp_func no_funcs[] = {
118 	{}
119 };
120 
121 static struct klp_object objs[] = {
122 	{
123 		.name = NULL,	/* vmlinux */
124 		.funcs = no_funcs,
125 		.callbacks = {
126 			.pre_patch = pre_patch_callback,
127 			.post_patch = post_patch_callback,
128 			.pre_unpatch = pre_unpatch_callback,
129 			.post_unpatch = post_unpatch_callback,
130 		},
131 	}, { }
132 };
133 
134 static struct klp_state states[] = {
135 	{
136 		.id = CONSOLE_LOGLEVEL_STATE,
137 		.version = CONSOLE_LOGLEVEL_STATE_VERSION,
138 	}, { }
139 };
140 
141 static struct klp_patch patch = {
142 	.mod = THIS_MODULE,
143 	.objs = objs,
144 	.states = states,
145 	.replace = true,
146 };
147 
148 static int test_klp_callbacks_demo_init(void)
149 {
150 	return klp_enable_patch(&patch);
151 }
152 
153 static void test_klp_callbacks_demo_exit(void)
154 {
155 }
156 
157 module_init(test_klp_callbacks_demo_init);
158 module_exit(test_klp_callbacks_demo_exit);
159 MODULE_LICENSE("GPL");
160 MODULE_INFO(livepatch, "Y");
161 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
162 MODULE_DESCRIPTION("Livepatch test: system state modification");
163